Reducing overheads of a protocol data unit in a wireless communication system

ABSTRACT

The present invention relates to transmitting data units of a radio protocol layer, wherein one logical channel identifier is added to one or more data units belonging to one logical channel. Because only one logical channel identifier is added to the data units belonging to one logical channel in constructing a MAC-e PDU, overheads of the MAC-e PDU are reduced. Such reduction of the PDU overheads increases data throughput, which is advantageous for a high-speed data communication system, such as the HSUPA.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.2004-0043757, filed on Jun. 14, 2004, the contents of which is herebyincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a medium access control (MAC) layer ofa mobile communications system and, more particularly, to a system andmethod for configuring data of the MAC layer.

BACKGROUND OF THE INVENTION

A universal mobile telecommunications system (UMTS) is athird-generation mobile communications system evolving from a globalsystem for mobile communications system (GSM), which is the Europeanstandard. The UMTS is aimed at providing enhanced mobile communicationsservices based on the GSM core network and wideband code-divisionmultiple-access (W-CDMA) technologies.

In December 1998, ETSI of Europe, ARIB/TTC of Japan, T1 of the UnitedStates, and TTA of Korea formed a Third Generation Partnership Project(3GPP) for creating detailed specifications of the UMTS technology.Within the 3GPP, in order to achieve rapid and efficient technicaldevelopment of the UMTS, five technical specification groups (TSG) havebeen created for determining the specification of the UMTS byconsidering the independent nature of the network elements and theiroperations.

Each TSG develops, approves, and manages the specification within arelated region. Among these groups, the radio access network (RAN) group(TSG-RAN) develops the specifications for the functions, requirements,and interface of the UMTS terrestrial radio access network (UTRAN),which is a new radio access network for supporting W-CDMA accesstechnology in the UMTS.

A related art UMTS network structure 1 is illustrated in FIG. 1. Asshown, a mobile terminal, or user equipment (UE) 2 is connected to acore network (CN) 4 through a UMTS terrestrial radio access network(UTRAN) 6. The UTRAN 6 configures, maintains and manages a radio accessbearer for communications between the UE 2 and the core network 4 tomeet end-to-end quality of service requirements.

The UTRAN 6 includes a plurality of radio network subsystems (RNS) 8,each of which comprises one radio network controller (RNC) 10 for aplurality base stations, or Node Bs 12. The RNC 10 connected to a givenbase station 12 is the controlling RNC for allocating and managing thecommon resources provided for any number of UEs 2 operating in one cell.One or more cells exist in one Node B. The controlling RNC 10 controlstraffic load, cell congestion, and the acceptance of new radio links.Each Node B 12 may receive an uplink signal from a UE 2 and may transmita downlink signals to the UE 2. Each Node B 12 serves as an access pointenabling a UE 2 to connect to the UTRAN 6, while an RNC 10 serves as anaccess point for connecting the corresponding Node Bs to the corenetwork 4.

Among the radio network subsystems 8 of the UTRAN 6, the serving RNC 10is the RNC managing dedicated radio resources for the provision ofservices to a specific UE 2 and is the access point to the core network4 for data transfer to the specific UE. All other RNCs 10 connected tothe UE 2 are drift RNCs, such that there is only one serving RNCconnecting the UE to the core network 4 via the UTRAN 6. The drift RNCs10 facilitate the routing of user data and allocate codes as commonresources.

The interface between the UE 2 and the UTRAN 6 is realized through aradio interface protocol established in accordance with radio accessnetwork specifications describing a physical layer (L1), a data linklayer (L2) and a network layer (L3) described in, for example, 3GPPspecifications. These layers are based on the lower three layers of anopen system interconnection (OSI) model that is well known incommunications systems.

A related art architecture of the radio interface protocol isillustrated in FIG. 2. As shown, the radio interface protocol is dividedhorizontally into a physical layer, a data link layer, and a networklayer, and is divided vertically into a user plane for carrying datatraffic such as voice signals and Internet protocol packet transmissionsand a control plane for carrying control information for the maintenanceand management of the interface.

The physical layer (PHY) provides information transfer service to ahigher layer and is linked via transport channels to a medium accesscontrol (MAC) layer. Data travels between the MAC layer and the physicallayer via a transport channel. The transport channel is divided into adedicated transport channel and a common transport channel depending onwhether a channel is shared. Also, data transmission is performedthrough a physical channel between different physical layers, namely,between physical layers of a sending side (transmitter) and a receivingside (receiver).

The second layer includes a MAC layer, a radio link control (RLC) layer,a broadcast/multicast control (BMC) layer and a packet data convergenceprotocol (PDCP) layer. The MAC layer maps various logical channels tovarious transport channels. The MAC layer also multiplexes logicalchannels by mapping several logical channels to one transport channel.The MAC layer is connected to an upper RLC layer via the logicalchannel. The logical channel can be divided into a control channel fortransmitting control plane information and a traffic channel fortransmitting user plane information according to the type of informationtransmitted.

The MAC layer is divided into a MAC-b sublayer, a MAC-d sublayer, aMAC-c/sh sublayer, a MAC-hs sublayer and a MAC-e sublayer according tothe type of transport channel being managed. The MAC-b sublayer managesa broadcast channel (BCH), which is a transport channel handling thebroadcast of system information. The MAC-c/sh sublayer manages commontransport channels such as an FACH (Forward Access Channel) or a DSCH(Downlink Shared Channel) that is shared by other terminals. The MAC-dsublayer handles the managing of a DCH (Dedicated Channel), namely, adedicated transport channel for a specific terminal. In order to supportuplink and downlink high speed data transmissions, the MAC-hs sublayermanages an HS-DSCH (High Speed Downlink Shared Channel), namely, atransport channel for high speed downlink data transmission, and theMAC-e sublayer manages an E-DCH (Enhanced Dedicated Channel), namely, atransport channel for high speed uplink data transmissions.

The RLC layer guarantees a quality of service (QoS) of each radio bearer(RB) and handles the transmission of corresponding data. The RLC layerincludes one or two independent RLC entities for each RB in order toguarantee a particular QoS of each RB. The RLC layer also provides threeRLC modes, namely, a Transparent Mode (TM), an Unacknowledged Mode (UM)and an Acknowledged Mode (AM), to support various types of QoS. Also,the RLC controls the size of data to be suitable for a lower layer intransmitting over a radio interface. For this purpose, the RLC segmentsand concatenates the data received from the upper layer.

A PDCP (Packet Data Convergence Protocol) layer is a higher layer of theRLC layer and allows the data transmitted through a network protocol(such as an IPv4 or IPv6) to be effectively transmitted over a radiointerface with a relatively small bandwidth. To achieve this, the PDCPlayer performs a header compression function wherein only necessaryinformation is transmitted in a header part of the data to therebyincrease transmission efficiency over the radio interface. Because thePDCP layer performs the header compression as a basic function, itexists only at a packet switched (PS) domain. One PDCP entity isprovided per RB to provide an effective header compression function withrespect to each PS service.

A BMC (Broadcast/Multicast Control) layer, located at an upper portionof the RLC layer in the second layer (L2), schedules a cell broadcastmessage and broadcasts the message to terminals located in a specificcell.

A radio resource control (RRC) layer located at the lowest portion ofthe third layer (L3) is defined in the control plane and controls theparameters of the first and second layers with respect to theestablishment, reconfiguration and release of RBs. The RRC layer alsocontrols logical channels, transport channels and physical channels.Here, the RB refers to a logical path provided by the first and secondlayers of the radio protocol for data transmission between the terminaland the UTRAN. In general, the establishment of the RB refers tostipulating the characteristics of a protocol layer and a channelrequired for providing a specific data service, and setting theirrespective detailed parameters and operation methods.

An HSUPA (High Speed Uplink Packet Access) will now be described indetail. The HSUPA is a system allowing a terminal or UE to transmit datato the UTRAN via the uplink at a high speed. The HSUPA employs anenhanced dedicated channel (E-DCH), instead of the related art dedicatedchannel (DCH), and also uses an HARQ (Hybrid ARQ) and AMC (AdaptiveModulation and Coding), required for high-speed transmissions, and atechnique such as a Node B-controlled scheduling.

For the HSUPA, the Node B transmits to the terminal downlink controlinformation for controlling the E-DCH transmission of the terminal. Thedownlink control information includes response information (ACK/NACK)for the HARQ, channel quality information for the AMC, E-DCHtransmission rate allocation information for the Node B-controlledscheduling, E-DCH transmission start time and transmission time intervalallocation information, transport block size information, and the like.

The terminal transmits uplink control information to the Node B. Theuplink control information includes E-DCH transmission rate requestinformation for Node B-controlled scheduling, UE buffer statusinformation, UE power status information, and the like. The uplink anddownlink control information for the HSUPA is transmitted via a physicalcontrol channel such as an E-DPCCH (Enhanced Dedicated Physical ControlChannel).

For the HSUPA, a MAC-d flow is defined between the MAC-d and MAC-e.Here, a dedicated logical channel such as a DCCH (Dedicated ControlChannel) or a DTCH (Dedicated Traffic Channel) is mapped to the MAC-dflow. The MAC-d flow is mapped to the transport channel E-DCH and thetransport channel E-DCH is mapped to the physical channel E-DPDCH(Enhanced Dedicated Physical Data Channel). The dedicated logicalchannel can also be directly mapped to the transport channel DCH. Inthis case, the DCH is mapped to the physical channel DPDCH (DedicatedPhysical Data Channel). Such inter-channel mapping relationships areshown in FIG. 3.

The MAC-d sublayer will now be described in detail. A transmitting sideMAC-d sublayer forms a MAC-d PDU (Protocol Data Unit) from a MAC-d SDUreceived from the upper layer, such as the RLC layer. A receiving sideMAC-d sublayer restores the MAC-d SDU from the MAC-d PDU received fromthe lower layer and delivers it to the upper layer, such as the RLClayer. At this time, the MAC-d sublayer exchanges the MAC-d PDU with theMAC-e sublayer through the MAC-d flow or exchanges the MAC-d PDU withthe physical layer via the DCH. The MAC-d sublayer performs a function,such as transport channel type switching for selectively switching atransport channel according to an amount of data, ciphering/decipheringfor performing ciphering or deciphering on the MAC-d PDU, TFC selectionfor selecting a transport format combination (TFC) suitable for achannel situation, and a C/T Mux for managing a logical channelidentifier (C/T) for identifying each dedicated logical channel whenseveral dedicated logical channels are multiplexed and are to be mappedto one DCH or to one MAC-d flow. A C/T field, such as a logical channelidentifier, is used only when a logical channel is multiplexed, andadded to a header of each MAC-d SDU to form the MAC-d PDU. Presently,the C/T field is defined to have 4 bits. Thus, the maximum number oflogical channels that can be multiplexed to one DCH or one MAC-d flow is16. The structure of the terminal, namely, the transmitting side of theMAC-d sublayer for the HSUPA, is shown in FIG. 4. A MAC-d format whenthe logical channels are multiplexed is shown in FIG. 5.

The transmitting side MAC-e sublayer forms the MAC-e PDU from the MAC-dPDU (namely, the MAC-e SDU), which is received through the MAC-d flowfrom the MAC-d sublayer. A receiving side MAC-e sublayer restores theMAC-e SDU from the MAC-e PDU received from the lower layer, namely, thephysical layer and delivers it to the upper layer. In this case, theMAC-e sublayer exchanges the MAC-e PDU with the physical layer via thetransport channel E-DCH.

The MAC-e sublayer performs a different function depending on whether itbelongs to the transmitting side or to the receiving side. First, thetransmitting side MAC-e sublayer performs a function ofscheduling/priority handling. Preferably, it schedules a datatransmission according to uplink/downlink control information andprocesses the data according to a priority level of the data. Thetransmitting side MAC-e also performs a function of hybrid ARQ, such asreliably transmitting data at a high speed, and a function of TFRC(Transport Format and Resource Combination) selection, such astransporting a format suitable for a channel situation and resourcecombination selection.

In particular, the scheduling/priority handling block also serves toform the MAC-e PDU to be transmitted to the physical channel.Specifically, the scheduling/priority handling block concatenates MAC-dPDUs (namely, MAC-e SDUs) received during a certain transmission timeinterval (TTI) through one MAC-d flow from the MAC-d sublayer accordingto their lengths. The scheduling/priority block then adds the lengthinformation to the MAC-e header, adds a 6-bit transmission sequencenumber (TSN) of the transport block to be transmitted to the header, andadds a 3-bit PID (Priority ID) for identifying a priority level of theMAC-d flow and a logical channel to the header. Finally, thescheduling/priority handling block adds a 1-bit version flag (VF) to theheader to form the MAC-e PDU in order to later support a different MAC-ePDU format.

The structure of the transmitting side MAC-e sublayer and the MAC-e PDUformat are shown in FIGS. 6 and 7. In general, a certain type of PDUformat is used so that the receiving side receives data as a series ofbit streams (e.g., 0, 1, 0, 1). Without determining a format, thereceiving side cannot interpret each bit for what it means. In theHSUPA, the MAC-e PDU format is used with some restrictions, as shown inFIG. 7. The restrictions are explained below.

First, one MAC-e PDU is transmitted during one TTI. Thus, a TSN is addedto every MAC-e PDU. Second, one MAC-e PDU includes only the data oflogical channels which belong to the same MAC-d flow and has the samepriority level. Thus, the PID is interpreted as a MAC-d flow ID+logicalchannel priority.

Third, the data of several logical channels are multiplexed to one MAC-ePDU in order to obtain multiplexing gain. In general, the length of theSDU can be different for each logical channel, so information indicatingthe length of each SDU is added to the header.

Of the above conditions, the length of the header of the MAC-e PDU isvaried due to the third condition. The length information of the SDUincludes three fields: a 3-bit SID (Size Index) field for indicating alength of each SDU, a 7-bit N field for indicating the number of SDUshaving the length of the SID, and a 1-bit F (Flag) field for indicatingwhether the next field is the SID length information or a MAC-e SDU.Preferably, the length information of the SDU includes the three fieldsof SID, N and F, and its size (length) increases to correspond with thenumber of length types of the SDU.

In order to wirelessly transmit a certain PDU via the physical channel,the PDU must have a determined length required for coding, modulationand spreading performed in the physical channel. Thus, the MAC-esublayer generates a PDU suitable for a size required by the physicalchannel by padding an end portion of the PDU. Such padding portionserves to fit the size of the PDU and does not contain any information.When the receiving side receives the PDU, it discards the paddingportion.

The receiving side interprets the received bit streams according to theformat shown in FIG. 7. Preferably, the receiving side interprets thebit streams starting from the VF (1 bit), PID (3 bits), TSN (6 bits),SID (3 bits), N (7 bits), F (1 bit), and interprets the header until theF field indicates that the next portion is the SDU. When the F fieldindicates that the next portion is the SDU, the receiving side, startingfrom the next bits, disassembles the SDU according to the lengthinformation of the SDU. Preferably, the SDU is disassembled according tothe length and the number of SDUs from the combination of SID, N and F.After extracting the SDU, a remaining portion is discarded as a paddingportion.

Notably, if the MAC-e SDU has the same length, the length information ofone SDU can be used to inform the lengths of other SDUs despite the useof several logical channels for transmitting data. With reference toFIG. 7, the first SDU length information, specifically, the combinationof SID1, N1 and F1, informs the data length of both a first logicalchannel (C/T=1) and a second logical channel (C/T=2), and Kth SDU lengthinformation, namely, the combination of SIDK, NK and FK informs the datalength from the fourth logical channel (C/T=4) to the kth logicalchannel (C/T=k). Preferably, the MAC-e sublayer does not process thedata by logical channel, but processes the data by the size of the MAC-eSDU.

The structure of the receiving side MAC-e sublayer is shown in FIG. 8.The HARQ block of the receiving side corresponds to the HARQ block ofthe transmitting side, and each HARQ process of the HARQ block performsan SAW (Stop And Wait) ARQ function with the transmitting side. When thereceiving side receives one MAC-e PDU through the HARQ process, it readsthe VF of the header of the MAC-e PDU to check its version, and checksthe next PID field to recognize which MAC-d flow and which prioritylevel the received PDU corresponds to. This operation is performed in are-ordering queue distribution block. The PDU is then delivered to areordering block indicated by the PID. The reordering function of thereceiving side is notable compared with the transmitting side. That is,the MAC-e sublayer receives the MAC-e PDUs through the HARQout-of-sequence, but the RLC layer (namely, the upper layer followingthe MAC-d sublayer) requests in-sequence delivery. Accordingly, theMAC-e sublayer performs reordering to sequentially deliver thenon-sequentially received PDUs to the upper layer.

To perform the reordering, each PID has a reordering buffer. Although acertain PDU is successfully received, if the TSN is not in sequence, thePDU is temporarily stored in the buffer. Then, when an in-sequencedelivery of the PDU is possible, it is delivered to the upper layer. Aportion from the TSN, except for the VF and the PID of the header of thePDU, is stored in the reordering buffer. Thereafter, when the PDU isdelivered to a disassembly block, the SDU is disassembled upon checkingthe SDU length information of the SID, N and F, and then delivered tothe upper MAC-d sublayer. Preferably, only the MAC-e SDU (MAC-d PDU) isdelivered through the MAC-d flow.

In the HSUPA, the structure of the MAC-d sublayer of the UTRAN (thereceiving side) is similar to the MAC-d sublayer of the terminal (thetransmitting side). Especially, portions of the receiving side relatedto the HSUPA perform the functions of the transmitting side, but inopposite order. As for the operations related to the DCH, the onlydifference is that the terminal performs the TFC selection, while theUTRAN performs the scheduling/priority handling. Referring to the HSUPA,regarding the MAC-d PDUs received through the MAC-d flow from the MAC-esublayer, the C/T Mux block reads the C/T field to detect which logicalchannel the data (i.e., MAC-d PDUs) belongs to, removes the C/T field,extracts the MAC-d SDU and delivers it via a channel indicated by theC/T field to the upper RLC layer. As aforementioned, the C/T field doesnot always exist, but exists when logical channels are multiplexed. Iflogical channels are not multiplexed, the received MAC-d PDU is theMAC-d SDU, so the C/T Mux block delivers such to the RLC layer. FIG. 9illustrates a structure of the MAC-d sub-layer of the UTRAN, thereceiving side in the HSUPA.

In the related art, numerous overheads are added in constructing theMAC-e PDU. Especially, when logical channels are multiplexed, the 4-bitC/T field (namely, the logical channel identifier) is added to eachMAC-e SDU. Thus, when numerous MAC-e SDUs are included in the MAC-e PDU,overheads of the MAC layer are considerably increased. Such increase inthe overheads leads to the reduction of throughput, therefore failing tomeet a desired transmission rate required for high speed datacommunication.

SUMMARY OF THE INVENTION

The present invention is directed to reducing overheads of a MAC-e PDU.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the presentinvention is embodied in a method for generating a protocol data unit ina wireless communication system, the method comprising receiving in afirst layer a plurality of service data units from a second layer,discriminating the plurality of service data units into groups based ona logical channel the service data units are received through, andgenerating the protocol data unit in the first layer, wherein theprotocol data unit comprises a header, the plurality of service dataunits from at least one group and a logical channel identifier for eachgroup, wherein each logical channel identifier identifies the logicalchannel each group of service data units is received through.

Preferably, the service data units of each group have the same size. Thediscrimination of the plurality of service data units occurs in thefirst layer. Alternatively, the discrimination of the plurality ofservice data units occurs in the second layer.

The logical channel identifier is added to the header. Alternatively,the logical channel identifier is added to a payload portion of theprotocol data unit. The protocol data unit is transmitted to a network.

Preferably, the first layer is a MAC-e layer. The second layer is aMAC-d layer. The logical channel identifier is a C/T field. Theplurality of service data units is a plurality of MAC-d SDUs.

Preferably, the header (MAC-e header) comprises length informationcomprising a size of the plurality of service data units receivedthrough each logical channel, wherein the length information comprisesat least one of an SID field, an N field, and an F field.

In accordance with another embodiment of the present invention, a methodfor generating a protocol data unit in a wireless communication systemcomprises receiving in a first layer at least one service data unit froma second layer and generating the protocol data unit in the first layer,wherein the protocol data unit comprises a header, the at least oneservice data unit and a logical channel identifier, wherein the logicalidentifier identifies the logical channel the at least one service dataunit is received through.

The logical channel identifier is added to the header. Alternatively,the logical channel identifier is added to a payload portion of theprotocol data unit. The protocol data unit is transmitted to a network.

Preferably, the first layer is a MAC-e layer. The second layer is aMAC-d layer. The logical channel identifier is a C/T field. The at leastone service data unit is at least one MAC-d SDU.

Preferably, the header (MAC-e header) comprises length informationcomprising a size of the at least one service data units receivedthrough the logical channel, wherein the length information comprises atleast one of an SID field, an N field, and an F field.

In accordance with another embodiment of the present invention, a mobileterminal for generating a protocol data unit in a wireless communicationsystem comprises means for receiving in a first layer a plurality ofservice data units from a second layer, means for discriminating theplurality of service data units into groups based on a logical channelthe service data units are received through, and means for generatingthe protocol data unit in the first layer, wherein the protocol dataunit comprises a header, the plurality of service data units from atleast one group and a logical channel identifier for each group, whereineach logical channel identifier identifies the logical channel eachgroup of service data units is received through.

Preferably, the service data units of each group have the same size. Thediscrimination of the plurality of service data units occurs in thefirst layer. Alternatively, the discrimination of the plurality ofservice data units occurs in the second layer.

The logical channel identifier is added to the header. Alternatively,the logical channel identifier is added to a payload portion of theprotocol data unit. The protocol data unit is transmitted to a network.

Preferably, the first layer is a MAC-e layer. The second layer is aMAC-d layer. The logical channel identifier is a C/T field. Theplurality of service data units is a plurality of MAC-d SDUs.

Preferably, the header (MAC-e header) comprises length informationcomprising a size of the plurality of service data units receivedthrough each logical channel, wherein the length information comprisesat least one of an SID field, an N field, and an F field.

In accordance with another embodiment of the present invention, a mobileterminal for generating a protocol data unit in a wireless communicationsystem comprises means for receiving in a first layer at least oneservice data unit from a second layer and means for generating theprotocol data unit in the first layer, wherein the protocol data unitcomprises a header, the at least one service data unit and a logicalchannel identifier, wherein the logical identifier identifies thelogical channel the at least one service data unit is received through.

The logical channel identifier is added to the header. Alternatively,the logical channel identifier is added to a payload portion of theprotocol data unit. The protocol data unit is transmitted to a network.

Preferably, the first layer is a MAC-e layer. The second layer is aMAC-d layer. The logical channel identifier is a C/T field. The at leastone service data unit is at least one MAC-d SDU.

Preferably, the header (MAC-e header) comprises length informationcomprising a size of the at least one service data units receivedthrough the logical channel, wherein the length information comprises atleast one of an SID field, an N field, and an F field.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. Features, elements, and aspects of the invention that arereferenced by the same numerals in different figures represent the same,equivalent, or similar features, elements, or aspects in accordance withone or more embodiments.

FIG. 1 illustrates a related a general UMTS network structure.

FIG. 2 illustrates a radio protocol architecture used in an UMTS.

FIG. 3 illustrates a MAC layer of a HSUPA.

FIG. 4 illustrates a structure of a MAC-d sublayer of a terminal.

FIG. 5 illustrates a format of a MAC-d PDU in multiplexing logicalchannels.

FIG. 6 illustrates a structure of a MAC-e sublayer of a transmittingside.

FIG. 7 illustrates a related art format of a MAC-e PDU.

FIG. 8 illustrates a structure of a MAC-e sublayer of a receiving side.

FIG. 9 illustrates a structure of a MAC-d sublayer of the UTRAN.

FIGS. 10A and 10B illustrate formats of a MAC-e PDU, in accordance withone embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to reducing overheads of a MAC-e PDU byeffectively processing a logical channel identifier (C/T field) added toeach MAC-d SDU. Preferably, a MAC-e sublayer processes data notaccording to SDU size, but according to logical channels. When the MAC-esublayer processes data according to logical channels, it is no longernecessary to add the logical channel identifier (C/T field) to eachMAC-d SDU. Thus, one common logical channel identifier can be added toevery MAC-d SDU transmitted via one logical channel. Accordingly,overheads due to the logical channel identifiers are considerablyreduced.

FIGS. 10A and 10B illustrate exemplary formats of a MAC-e PDU inaccordance with a preferred embodiment of the present invention. TheMAC-e PDU formats may differ depending on where the common logicalchannel identifier is added. Preferably, the common logical channelidentifier may be added to a payload portion of the MAC-e PDU as shownin FIG. 10A, or may be added to a header as shown in FIG. 10B.

Although only two formats are shown in FIGS. 10A and 10B, other formatscan be formed according to how the position of the logical channelidentifier is defined. Preferably, in case of adding the logical channelidentifier to the payload, it may be added after the logical channeldata, rather than before the data. In case of adding the logical channelidentifier to the header, it may be added between the SID and N, orbetween N and F, or after F, not only before the SID, N and F. In anycase, the logical channel identifier is added once with respect to onelogical channel, and its position must be previously defined so that thereceiving side can decode it properly.

Preferably, when using one or more MAC-e PDU formats in accordance withthe present invention, the following points are noted. First, the SDUlength information (SID, N, F) is added to a header for each logicalchannel regardless of the size of the SDU. Preferably, the SDU lengthinformation is added to logical channel data even though the logicalchannel data have the same size. Considering that a total of 11 bits ofSDU length information are to be added so as to correspond to the numberof logical channels despite the SDUs being the same size, the presentinvention initially appears to be ineffective. However, because the4-bit C/T field is reduced for every MAC-e SDU, if four or more MAC-eSDUs belong to one logical channel, overhead production will beminimized.

Second, the size of the SDU indicated by the SID corresponds to the sizeof the MAC-d SDU excluding the C/T field. Since the SDU size indicatesonly the MAC-d SDU size, when the transmitting side or the receivingside adds or interprets the SID, a value excluding the C/T field isused.

Third, because the C/T field is added or separated, the function of theC/T Mux block in the MAC-d sublayer and the function of thescheduling/priority handling block or the disassembly block in the MAC-esublayer is affected. Specifically, in the present invention, one C/Tfield is added to every MAC-d SDU which belongs to one logical channeland is transmitted together through the MAC-d flow. Thescheduling/priority handling block of the transmitting side MAC-esublayer combines the received MAC-d SDUs by logical channel andconstructs a MAC-e PDU by adding the logical channel identificationinformation to a determined position.

When the disassembly block of the receiving side MAC-e sublayertransmits data to the MAC-d sublayer through the MAC-d flow, ittransmits the data in units of MAC-d SDUs, not in units of MAC-d PDUs.The MAC-e sublayer then delivers one C/T field with respect to the MAC-dSDUs. The MAC-d SDUs are delivered together in order to discriminatelogical channels of the MAC-d SDUs. Upon receipt, the C/T Mux of thereceiving side MAC-d sublayer transfers the MAC-d SDUs, which have beenreceived together, to a logical channel indicated by the C/T field,which has also been received therewith.

As so far described, the system and method for configuring data of theMAC layer in accordance with the present invention has the followingadvantages. Because only one logical channel identifier is added to thedata belonging to one logical channel when constructing a MAC-e PDU,overheads of the MAC-e PDU are reduced. Such reduction of the PDUoverheads increases the data throughput, which is advantageous for ahigh-speed data communication system such as the HSUPA.

Although the present invention is described in the context of mobilecommunication, the present invention may also be used in any wirelesscommunication systems using mobile devices, such as PDAs and laptopcomputers equipped with wireless communication capabilities. Moreover,the use of certain terms to describe the present invention should notlimit the scope of the present invention to certain type of wirelesscommunication system. The present invention is also applicable to otherwireless communication systems using different air interfaces and/orphysical layers, for example, TDMA, CDMA, FDMA, WCDMA, etc.

The preferred embodiments may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Field Programmable Gate Array (FPGA), Application SpecificIntegrated Circuit (ASIC), etc.) or a computer readable medium (e.g.,magnetic storage medium (e.g., hard disk drives, floppy disks, tape,etc.), optical storage (CD-ROMs, optical disks, etc.), volatile andnon-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs,SRAMs, firmware, programmable logic, etc.).

Code in the computer readable medium is accessed and executed by aprocessor. The code in which preferred embodiments are implemented mayfurther be accessible through a transmission media or from a file serverover a network. In such cases, the article of manufacture in which thecode is implemented may comprise a transmission media, such as a networktransmission line, wireless transmission media, signals propagatingthrough space, radio waves, infrared signals, etc. Of course, thoseskilled in the art will recognize that many modifications may be made tothis configuration without departing from the scope of the presentinvention, and that the article of manufacture may comprise anyinformation bearing medium known in the art.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuredescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method for processing data units of a wireless communication systemcomprising a terminal and a radio access network, the method performedby the terminal comprises: receiving a plurality of service data unitsfrom a first layer; concatenating the plurality of received service dataunits; adding a header to the concatenated service data units togenerate a protocol data unit, and delivering the generated protocoldata unit to a second layer, wherein the generated protocol data unitfor High Speed Uplink Packet Access (HSUPA) comprises: the concatenatedplurality of service data units classified into at least two groups,each group having service data units belonging to each logical channel,and service data units belonging to one logical channel having a samesize, each logical channel identifier information included for eachgroup, and each length information included for each group, indicating asize of the service data units belonging to each logical channelexcluding a size of each logical channel identifier information, whereineach logical channel is located between a radio link control (RLC) layerand a medium access control (MAC) layer, wherein the MAC layer comprisesthe first layer and a third layer, wherein the first layer is for adedicated channel (DCH) and the third layer is for an enhanced dedicatedchannel (E-DCH), wherein the concatenation of the plurality of receivedservice data units is performed by the third layer, wherein each logicalchannel identifier information is included in the header of the protocoldata unit, and wherein the header of the protocol data unit is added bythe third layer.
 2. The method of claim 1, wherein each lengthinformation comprises size information (SID) indicating a size of oneservice data unit.
 3. The method of claim 1, wherein the generatedprotocol data unit is delivered to the second layer via the E-DCH. 4.The method of claim 3, wherein each length information further comprisesnumber information (N) indicating a number of the service data unitsbelonging to each logical channel.
 5. The method of claim 1, wherein thesteps are performed by a medium access control (MAC) layer.
 6. Themethod of claim 1, wherein each length information are included in theheader of the generated protocol data unit.
 7. The method of claim 6,wherein each length information is included in the header of thegenerated protocol data unit regardless of the size of the service dataunits belonging to each logical channel.
 8. The method of claim 1,wherein the first layer is a MAC-d layer and the second layer is aphysical layer.
 9. The method of claim 1, wherein the third layer is aMAC-e layer.
 10. A method for processing data units of a wirelesscommunication system comprising a terminal and a radio access network,the method performed by the network comprises: receiving a protocol dataunit including a header and a plurality of concatenated service dataunits from a second layer in a receiving unit; reading the header of thereceived protocol data unit in a reading unit; disassembling theplurality of concatenated service data units; and delivering thedisassembled service data units in a disassembling unit to a first layerin a delivering unit, wherein the received protocol data unit for HighSpeed Uplink Packet Access (HSUPA) comprises: the plurality ofconcatenated service data units classified into at least two groups inthe terminal, each group having service data units belonging to eachlogical channel, and service data units belonging to one logical channelhaving a same size, each logical channel identifier information includedfor each group, and each length information included for each group,indicating a size of the service data units belonging to each logicalchannel excluding a size of each logical channel identifier information,wherein each logical channel is located between a radio link control(RLC) layer and a medium access control (MAC) layer wherein the MAClayer comprises the first layer and a third layer, wherein the firstlayer is for a dedicated channel (DCH) and the third layer is for anenhanced dedicated channel (E-DCH), wherein the disassembling of theplurality of concatenated service data units is performed by the thirdlayer, wherein each logical channel identifier information is includedin the header of the protocol data unit, and wherein the header of theprotocol data unit is read by the third layer.
 11. The method of claim10, wherein each length information comprises size information (SID)indicating a size of one service data unit.
 12. The method of claim 10,wherein the protocol data unit is received via the E-DCH.
 13. The methodof claim 12, wherein each length information further comprises numberinformation (N) indicating a number of the service data units belongingto each logical channel.
 14. The method of claim 10, wherein the stepsare performed by a medium access control (MAC) layer.
 15. The method ofclaim 10, wherein each length information are included in the header ofthe protocol data unit.
 16. The method of claim 15, wherein each lengthinformation is included in the header of the protocol data unitregardless of the size of the service data units belonging to eachlogical channel.
 17. The method of claim 10, wherein the first layer isa MAC-d layer and the second layer is a physical layer.
 18. The methodof claim 10, wherein the third layer is a MAC-e layer.